Bovine mastitis is the most common and most costly disease affecting dairy herds. Some estimates suggested at least half of the dairy animal population have some degree or form of mastitis. This condition results in lowered milk yield and reduced quality. Economic loss to mastitis in the U.S. is estimated at about $1.8 billion or approximately 10% of total milk sales with about two-thirds of this loss due to reduced milk production from infected cows. Mastitis is an inflammation of the mammary gland. Similarly, inflammation is one response of a tissue or organ to insult or injury. An injury caused by physical, chemical or thermal trauma can produce an inflammatory response. In the dairy cow, mastitis typically results from microorganisms, usually bacteria, that invade the udder, multiply in the delicate milk producing tissues, and synthesize toxins, a by-product of bacterial metabolism. The characteristic features of inflammation are swelling, heat, redness, pain and disturbed function.
While the animal immune system can fight intramammary infections, many chronic infections remain sub-clinical (asymptomatic) and undetected unless diagnosed by laboratory testing. Sub-clinical mastitis can result in a reservoir of micro-organisms that leads to the infection of other animals within the herd. More than 80 species of microorganisms have been identified as causal agents, although approximately 95% of mastitis is caused by four pathogens; Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysagalactiae, and Streptococcus uberis. Mastitis causing pathogens fall into two categories namely contagious and environmental. Contagious bacteria, such as Streptococcus agalactiae and Staphylococcus aureus, primarily colonize host tissue sites such as mammary glands, teat canals, teat skin lesions etc. and are spread from one infected cow to another during the milking process. Environmental bacteria, often streptococci, enterococci and coliform organisms, are commonly present within the cow's surroundings from sources such as cow feces, soil, plant material, bedding or water, and infect by casual opportunistic contact with an animal during the inter-milking period. This distinction, although not exclusive, is of practical importance because different dairy herd maintenance measures are needed for the different groups of microorganisms. In all bovine mastitis cases, whatever the causal microorganism, the route of transmission of the invading pathogen into the inner gland of the udder is through the teat orifice and teat canal.
Management of dairy herds focuses attention on treatment of both established mastitis and on prevention of new intramammary infections. Therapy and hygiene are the two fundamental components of an effective mastitis control protocol. Each is applied in concert, and each operates independently. The primary effect of therapy is to increase the rate of eliminating established infections; whereas, hygiene reduces the frequency of infection by interrupting transmission vectors. We cannot present all ancillary factors that may be employed for the elimination and prevention of mastitis, however, the most effective therapy and hygiene practices are, respectively, antibiotic infusion treatment of the udder's four quarters at the end of lactation; and, post-milking teat antisepsis or “teat dipping” during lactation.
Researchers agree, and an abundance of published evidence supports the concept, that dipping teats into an effective antimicrobial solution immediately after each milking is the single most effective procedure for decreasing new intramammary infections in lactating cows. Between 1955 to 1970, Dodd and co-workers (F. K. Neave, F. H. Dodd, and R. G. Kingwell, 1966, “A Method of Controlling Udder Disease”, Vet. Rec. 78:521; F. K. Neave, F. H. Dodd, R. G. Kingwell and D. R. Westgarth, 1969, “Control of Mastitis in the Dairy Herd by Hygiene and Management”, J. Dairy Sci. 52:696; F. H. Dodd, D. R. Westgarth, F. K. Neave and R. G. Kingwill, 1969, “Mastitis—The Strategy of Control”, J. Dairy Sci. 52:689; and F. H. Dodd, and F. K. Neave, 1970, “Mastitis Control”, Proceedings, Nat'l. Inst. Res. Dairying, pp. 21-60) conducted extensive epidemiologic investigations in commercial dairy herds. From this work, they developed the conceptual basis for modern mastitis control methods of which teat dipping is an integral component. The efficacy and value of teat dipping has since been confirmed in dozens of field trials, and it is now accepted that an effective teat dip can reduce the incidence of new intramammary infections at least 50% and often up to 90%.
To reduce mastitis, commercial teat dips have been developed containing a variety of antimicrobial agents including iodophors, quaternary ammonium compounds, chlorhexidine salts, chlorine release compounds (e.g. alkali hypochlorites), oxidizing compounds (e.g. hydrogen peroxide, peracids), protonated carboxylic acids (e.g. heptanoic, octanoic, nonanoic, decanoic, undecanoic acids), acid anionics (e.g. alkylaryl sulfonic acids), and chlorine dioxide (from chlorite). These agents, which have varying degrees of effectiveness, limit the transmission of mastitis by reducing pathogen populations on the teat. Teat dips, can also be divided into two broad classifications. The Class I type are antimicrobial and are applied to kill microorganisms already present in the teat canal or on the surface of the teat skin. By design, their microbiological effect is immediate and their targets primarily the contagious organisms that are vectored between animals during the pre-milking, milking and post milking process. The Class II type teat dip, often referred to as a “teat sealer,” is a film-forming or coating composition which may or may not be antimicrobial; and, functions by developing a residual protective barrier on the teat thus providing prophylaxis by sealing the teat off from its environment. The film which forms on the surface of the teat serves as a physical barrier through which mastitis causing pathogens cannot penetrate during the intermilking period.
General disclosures of teat dip technology are shown in: “Current Concepts of Bovine Mastitis.” 1996, Fourth Ed. National Mastitis Council, Madison Wis.; P. A. Murdough and J. W. Pankey, 1993. “Evaluation of 57 Teat Sanitizers Using Excised Cow Teats”, J. Dairy Sci. 76:2033-2038; J. W. Pankey et al., 1984, “Uptake on Post-milking Teat Antiseptics”, J. Dairy Sci. 67:1336-1353; R. J. Farnsworth, 1980, “Role of Teat Dips in Mastitis Control”, J. Am. Vet. Med. Assoc. 76:1116-1118; W. N. Philpot, 1979, “Control of Mastitis by Hygiene and Therapy”, J. Dairy Sci. 62:168-176; W. N. Philpot and J. W. Pankey, 1978, “Hygiene in the Prevention of Udder Infections V. Efficacy of Teat Dips Under Experimental Exposure to Mastitis Pathogens”, J. Dairy Sci. 61:956-963; R. P. Natzke, 1977, “Role of Teat Dips and Hygiene is Mastitis Control”, J. Amer. Vet. Med. Assoc. 170:1196-1198; W. N. Philpot and J. W. Pankey, 1975, “Hygiene in the Prevention of Udder Infections. III. Effectiveness of 59 Teat Dips for Reducing Bacterial Populations on Teat Skin”, J. Dairy Sci. 58:209-216; R. J. Eberhart and J. M. Buckalew, 1972, “Evaluation of a Hygiene and Dry Period Therapy Program for Mastitis Control”, J. Dairy Sci. 55:1683-1691; W. D. Schultze and J. W. Smith, 1972, “Effectiveness of Postmilking Teat Dips”, J. Dairy Sci. 55:426-431; D. P. Wesen and L. H. Schultz, 1970, “Effectiveness of a Post-Milking Teat Dip in Preventing New Udder Infections”, J. Dairy Sci. 53:1391-1403; and British Pat. No. 1,144,637 (Kelco Chemicals Ltd.), published Mar. 5, 1969. U.S. Pat. No. 4,199,602 (Lentsch) issued Apr. 22, 1980, U.S. Pat. No. 4,258,056 (Lentsch) issued Mar. 24, 1981; and U.S. Pat. No. 4,376,787 (Lentsch) issued Mar. 15, 1983 disclose nitroalkanol, amino carboxylate/sulfonate, and sulfonate based compositions. U.S. Pat. No. 4,446,153 (Yang) issued May 1, 1984 discloses a benzyl alcohol/phenyl ethanol based composition.
Typical disclosures of intermilking or protective (barrier-type) film-forming teat dips or teat “sealers” can be found in Akers et. al., U.S. Pat. No. 3,066,071, issued Nov. 27, 1962; Kraus, U.S. Pat. No. 3,222,252, issued Dec. 7, 1965 (but, see Philpot et. al., J. Dairy Science 58:205-216); Coughman and Brown, U.S. Pat. No. 3,993,777, issued Nov. 23, 1976; Pugliese, U.S. Pat. No. 4,049,830, issued Sep. 20, 1977; and Andrews et al., U.S. Pat. No. 4,113,854, issued Sep. 12, 1978. A teat sealer similar or identical to the Andrews et. al. film-forming composition is in commercial use and has been discussed in the dairy science literature. See, for example, R. J. Farnsworth et. al., 1980, “Use of a Teat Sealer for Prevention of Intramammary Infections in Lactating Cows”, J. Am. Vet. Med. Assoc. 177:441-444; and R. J. Farnsworth et. al., 1981, “The Effect of a Teat Sealer on Coliform Mastitis”, The Bovine Practitioner, No. 16, pp. 28-29. Still further examples of barrier-type film-formers for bovine teats can be found in Silver et al., U.S. Pat. No. 4,199,564, issued Apr. 22, 1980; Dybas et al., U.S. Pat. No. 4,311,709, issued Jan. 19, 1982; Marhavka, U.S. Pat. No. 5,017,369, issued May 21, 1991; and Schmidt et al., U.S. Pat. No. 5,503,838, issued Apr. 2, 1996.
Persons skilled in the art of bovine mastitis treatment know that antimicrobial teat dip compositions (Class I type) which do not form protective films with barrier properties have a shortened residual time on the teat and their efficacy is quickly lost due to adsorption, ion-pairing, oxidation or simply sloughing off. Furthermore, such teat dips often fail to retard the entrance of bacteria into the teat canal during the intermilking period and provide no protection to the teat from irritation caused by wind, sun or contact abrasion. As disclosed in the art, attempts have been made to provide antimicrobial teat dips containing film-forming materials designed to form protective barriers on the skins of the teats; and, to afford continuous protection against mastitis causing pathogens, both contagious and environmental, and, from irritation caused by exposure to adverse environmental elements.
Early researchers discovered that incorporating a film-forming, protective barrier system into an antimicrobial teat dip was fraught with technical problems, either physicochemical problems with the composition or application/performance problems in practice. The best prophylactic barriers, and most environmentally durable, are water insoluble synthetic organics made up of homopolymers or heteropolymers of two or more different monomers. These are applied either from volatile solvent based compositions or by film-forming polymer latexes which are suspensions of a water insoluble polymer in water. U.S. Pat. No. 3,066,071 typifies the former type; and U.S. Pat. No. 4,113,854 discloses compositions typical of the latter kind. Typically, barrier films formed upon teats when applied from a volatile solvent based mastitis dip composition are not user, animal or environmentally friendly. In practice, these materials subject the skin of the teat to the drying, irritating effects of organic solvents. Compositions containing a film-forming polymer latex overcome volatile solvent concerns as polymer latexes are most often suspensions of a water insoluble polymer(s) in water; however, commercial latexes necessarily include stabilizers, preservatives, suspending agents etc. which add complexity; and, as such are frequently incompatible with the most preferred and most efficacious antimicrobial agents. All water insoluble polymeric films, which generally form a flexible almost rubbery film on the teat skin, must be removed by peeling. In practice, such mastitis control compositions have not received widespread acceptance because of the inconvenient, time-consuming, often troublesome removal process prior to milking.
U.S. Pat. No. 3,222,252 describes a bovine teat dip consisting of vegetable oils of the drying or semi-drying types and certain fatty acid esters. In concept, this disclosure bridges the gap between synthetic polymer coatings and natural polymer coatings. In practice, oil based dips have proved to be ineffective in preventing mastitis, and they are difficult to remove from the teats. In fact, their use has tended to increase the incidence of mastitis (see Philpot et. al, J. Dairy Science 58:205-216).
U.S. Pat. No. 3,993,777, referenced above, discloses an aqueous thickened quat based formulation of high viscosity containing emollients such as lanolin and glycerin. The material forms a protective film and bacteriostatic barrier about the teat which is easily removed by washing; thus, transitioning from water insoluble protective films which in practice are peeled from the teat to water washable films. However, the shortfall of this teaching is the use of hydroxyethylcellulose employed as a thickener (its most typical function) in the preferred formulation which, by chance, has the characteristic of forming pliable non-brittle films upon drying. In herd practice, such cellulosic thickeners seldom perform the dual-function role of providing a tenacious barrier, being too readily removed because of its water-sensitivity, wherein the performance of the antimicrobial barrier is lost. U.S. Pat. No. 4,311,709 also discloses a film-forming methycellulose having similar disadvantage as a teat dip barrier. U.S. Pat. No. 4,049,830 discloses a bovine teat dip composition which delivers an oil-in-water emulsion to the teat and, upon drying, forms an antimicrobial lipid solids barrier which remains soft and tacky for prolonged periods and is water washable. Herd experience has shown that soft barriers are too easily abraded or otherwise sloughed off during the intermilking period with subsequent reduction or loss of biocidal function. U.S. Pat. No. 5,017,369 discloses antimicrobial mastitis treatment compositions which utilize a water resistant film-forming agent, polyvinyl alcohol. This art teaches away from incorporation and use of thickener admixtures, suggesting that adequate viscosity can be obtained simply by adjusting the amount of polyvinyl alcohol in the composition. Such compositions are, in application, at commercial disadvantage because polyvinyl alcohol by itself does not provide effective teat cling nor does it decrease the mobility of the dipping liquid which is manifested by excessive drain-off and loss of product; and, therefore significant reduction of barrier function and microbial performance. U.S. Pat. No. 5,503,838 overcomes this disadvantage in disclosing antimicrobial teat dip compositions containing polyvinyl alcohol in cooperation with thickening agents such as a xanthan gum. Unfortunately, neither U.S. Pat. No. 5,017,369 which typically embodies chlorhexidene gluconate or quaternary ammonium compounds as the antimicrobial; nor, U.S. Pat. No. 5,503,838 which uses iodine as the preferred biocidal agent, address the issue of teat dermal irritation caused by residual barrier films containing resident, chemically aggressive, often toxic, antimicrobial agents which remain on skin contact for extended periods of time.
Alliger, U.S. Pat. No. Re. 31,779, reissued Dec. 25, 1984; Alliger, U.S. Pat. No. 4,330,531 (Alliger) issued May 18, 1982; Kross et al., U.S. Pat. No. 4,891,216, issued Jan. 2, 1990; Davidson et al., U.S. Pat. No. 4,986,990, issued Jan. 22, 1991; Davidson et al., U.S. Pat. No. 5,185,161, issued Feb. 9, 1993; and Kross, U.S. Pat. No. 5,597,561 disclose technology embodied in a commercial composition sold as an antimicrobial barrier teat dip under the name UDDER-GOLD PLUS (Alcide Corp., Redmond, Wash.). The patents disclose two aqueous solutions, described as gels, adapted to be mixed in a 50/50 proportion wherein (according to patent and product literature) chlorous acid/chlorine dioxide are generated by chemical reaction of I-hydroxy-benzene-acetic acid (mandelic acid) and sodium chlorite present in first and second gels respectively. The second gel can contain a thickener. Later patents disclose a homopolymer of 2-acrylamido-2-methylpropane sulfonic acid (polysulfonic acid) which forms a protective film over the teat. Although this composition has proven effective, it is not without problem. The herdsman is advised to mix and use the admixture for only one herd milking, discarding any extra. This attribute is likely a consequence of chlorine dioxide loss (hence, loss of antimicrobial efficacy) either from chemical incompatibility and/or off-gassing. The polysulfonic acid “gelling agent” does not immobilize the treatment on the teat and significant drippage/waste occurs. U.S. Pat. No. 5,597,561 teaches that polysulfonic acid has proven problematic because of its strong affinity to the dermal tissue and tendency to form a solid matrix which is difficult to remove by washing.
Richter, U.S. Ser. Nos. 08/038,064 and 08/038,553, and U.S. Pat. No. 6,379,685, disclose basic teat dip technology. These systems are two part chlorite and acid materials that when blended form a protective layer or coating. The utility or effectiveness of these systems can be enhanced by the presence of a marker dye showing the location of the treatment on or adhering to the animal. Simply including a dye in the chlorite part, however, or in the combined materials, is often not fully effective. The oxidizing nature of chlorite (ClO2−1) or chlorine dioxide (ClO2) can rapidly alter or bleach the typical added color.
A substantial need remains after all these attempts, for long lasting protective, film or shield forming barrier-type teat dip compositions having a visual indicator or unique color that can indicate the presence of an immediate and long lasting antimicrobial effect against a wide spectrum of mastitis causing organisms. The visual indicator can also indicate the presence of an active effective amount of ClO2.